Age has been the risk factor most consistently associated with the development of tardive dyskinesia (TD). Increased rates of prevalence, severity and persistence of TD are associated with increasing age. Interpretation of true prevalence rates is complicated by reports of idiopathic spontaneously occurring movement disorders in the elderly. Additionally, elderly persons may suffer from serious medical conditions which may predispose them to develop drug-induced or spontaneous movement disorders. To evaluate the incidence, outcome of and vulnerability to movement disorders in the elderly, 400 patients over the age of 55 will be evaluated prospectively while receiving neuroleptic treatment. Half the sample will be starting on neuroleptics for the first time at study entry and half will have had prior neuroleptic exposure; however, these will have been neuroleptic-free for at least one month. After a drug-free baseline assessment, patients will be reexamined every three months for 4 years. Medication will be withdrawn every six months to assess covert TD. Patients meeting criteria for abnormal movement case definition will receive a medical and neurological work-up to identify possible alternative causes of the movement disorder.